Power storage devices such as secondary batteries have conventionally been used as a power source of an electric vehicle (EV), a hybrid electric vehicle (HEV), and a fuel cell vehicle (FCV). To satisfy the need for high power, an assembled battery is provided by electrically connecting a plurality of unit cells in series (see, for example, Patent Document 1).
[Patent Document 1] Japanese Patent Publication No. 2004-164897 (FIG. 1)